This invention relates to a video signal receiver for a near video-on-demand broadcast system.
Commonly, video programming has been provided to consumers through fundamentally different distribution systems. In one, video programs are recorded on individual video cassette tapes (or video discs) which are sold or rented to consumers. Conveniently, the consumer may view the recorded video program at the time of his choosing and may pause (or temporarily halt) reproduction of the video program at any time for an arbitrary length of time. However; a major disadvantage of this system is that the distributor lacks effective control over the dissemination of the video cassette tape or disc to other consumers by secondary sale of the cassette tape or disc or by copying of the video program to another cassette tape. Consequently, the distributor is unable to collect a royalty payment for each reproduction of the video program.
In television transmission systems, such as cable television distribution systems, cable operators provide pay-per-view services whereby subscribers may order a specific video program for viewing at its predetermined broadcast time. Typically, the desired program is broadcast one or more times per day and in some systems may be broadcast repetitively at consecutive intervals. After charging the subscriber a given fee, the cable operator activates the subscriber's individually-addressable cable decoder box to decode the ordered programming for ordinary reception and display. Without the benefit of a recording device, the subscriber's viewing of the video program is limited to the specific interval during which the program is broadcast. All too often, the broadcast schedule for the particular program is incompatible with the subscriber's own personal schedule. Further, the subscriber is constrained to view the entire program during one sitting as there is no mechanism for pausing or otherwise interrupting display of the video program. Such a feature is needed to facilitate viewing of a program in discrete intervals and to accommodate interruptions, such as a telephone call, during display of the program.
Introduction of satellite broadcast digital video signal transmission capabilities coupled with efficient data compression techniques has enabled the digital transmission of several video program signals in the same bandwidth as a single broadcast analog video signal. Such technology is incorporated into a "near video-on-demand" service, also called a "time interval transmitting system," in which a single video program is broadcast on multiple channels with a short interval between the starting time of each program broadcast. For example, a two-hour movie may be broadcast on seven consecutive channels with the starting broadcast time of each channel offset by fifteen minutes from that of a neighboring channel, such that the beginning of the movie is effectively available on one of the channels once every fifteen minutes. Thus, by transmitting the same program at predetermined intervals on a plurality of channels, the maximum time a subscriber will wait between ordering and viewing a prescheduled broadcast video program will be equal to the broadcast interval between channels. By definition, this broadcast interval is much shorter than the period between consecutive broadcasts of a program on a single channel of a pay-per-view system.
Further, a near video-on-demand service can utilize other data compression techniques to reduce the time required to transmit a video program to a fraction of the actual running time of the program. By reducing the transmission time of a program, fewer channels can be used to transmit the program at consecutive intervals and/or the transmission interval between channels can be reduced.
However, the near video-on-demand system still suffers the drawback of not providing a "pause" function which allows the viewer to interrupt display of the video program for a period of time. As an awkward alternative, it is contemplated that a viewer could attempt to manually implement a pause-type function after a viewing interruption by scanning other channels carrying the program for a segment of the program which the viewer remembers as preceding the interruption. Assuming proper channel selection, the amount of program that will necessarily be viewed twice (i.e., the overlap) will depend upon the duration of the viewing interruption but will not be greater than the interval between broadcasts. Clearly, such a solution is less than optimal.
Another deficiency of the near video-on-demand system is the variable delay between a subscriber's ordering of a program and the availability of that program for viewing. Similar to the above, the variable delay will be no greater than the broadcast interval. Certainly, the inherent delay makes such a system less convenient than a video-on-demand system which displays the desired video programming immediately.